arXiv:2606.05973v2

Liouville-Preserving Hamiltonian Scattering on Finite Metric Graphs

Philip Hierhager

math-phmath.DS37J0570H0537A1034B45

Abstract

A metric graph with a mechanical Hamiltonian on each edge does not, by itself, define a deterministic classical motion through a branching vertex: conservation of energy fixes only the outgoing speed, not the outgoing edge-end. We study the deterministic problem obtained after this missing vertex datum is supplied. On each edge ee, with coordinate q[0,e]q\in[0,\ell_e], the Hamiltonian is He(q,p)=p2/2+Ve(q)H_e(q,p)=p^2/2+V_e(q), where VVis continuous on the graph and C2C^2 on every edge. At each vertex we prescribe an energy-preserving Borel isomorphism from incoming to outgoing nonzero boundary covectors. The resulting phase space is the measurable quotient that identifies each incoming boundary covector with its prescribed outgoing one. After excluding the finitely many energy levels V(v)V(v), the edgewise Hamilton equations and the vertex laws concatenate to a global one-parameter group of bimeasurable transformations. The group preserves energy and the quotient measure induced by the edgewise Liouville measures dqdpdq\,dp. The proof uses no smooth symplectic structure on the quotient; the invariance follows from ordinary edgewise Liouville invariance, a uniform no-Zeno estimate on compact regular energy windows, and preservation of the transverse Liouville flux rdrr\,dr by the speedwise vertex permutations. If the vertex laws are compatible with momentum reversal, then the quotient dynamics is reversible. On regular energy surfaces satisfying the usual regular-value condition, the induced time-parametrization measure is invariant as well.

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Audited against arXiv v2

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

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Generated August 18, 2026
01Statements2 reported findingsCorrect

The construction of a global deterministic scattered flow on the regular phase-space quotient, its Liouville invariance and reversibility, and invariance of the regular-energy time measure are correct.

Theorem VI.5, Corollary VI.6, and Proposition VII.1Correct

Energy-preserving vertex permutations preserve the global Liouville flow

Pages 21–27 · Theorem VI.5, Corollary VI.6, and Proposition VII.1 · arXiv:2606.05973v2

At fixed nonzero speed, any energy-preserving Borel bijection is a permutation of the finitely many incident edge-ends, hence preserves the transverse flux measure rdrr\,dr. Edgewise Hamiltonian evolution preserves dqdpdq\,dp, and the quotient identification matches equal flux on incoming and outgoing sections. On compact energy windows avoiding all vertex values, transit times have a uniform positive lower bound, excluding Zeno accumulation and yielding a two-sided measurable flow. Momentum compatibility gives the stated reversing involution.

Full paper, version 2
Corollary VI.6 and Proposition VII.1Correct

Reversibility and invariant energy-surface time measure follow from the global flow

Sections VI–VII · arXiv:2606.05973v2

Momentum reversal conjugates every local scattering map to its inverse, so it reverses the quotient flow. On a regular energy surface, travel time contributes density dq/2(EV(q))dq/\sqrt{2(E-V(q))} on each directed edge, and the flux matching at vertices is exactly the energy-preserving scattering condition.

02Proofs2 reported findingsCorrect

The quotient, no-Zeno, measurability, flux-balance, and energy-disintegration proofs are correct and complete.

Sections III–VIICorrect and complete

The measurable quotient needs no unproved symplectic structure

Pages 8–27 · Sections III–VII · arXiv:2606.05973v2

The equivalence relation pairs each incoming covector with one outgoing covector and remains Borel because only finitely many edge-ends occur. Successive hitting times are measurable, finite concatenations preserve Liouville measure by ordinary flow boxes, and the no-Zeno bound permits passage to arbitrary time. Coarea on each edge gives the regular-energy density used in Proposition VII.1.

Sections V–VIICorrect and complete

No-Zeno continuation and vertex-flux cancellation make the global construction complete

Pages 24–43 · arXiv:2606.05973v2

Uniqueness of each scattering continuation is compatible with the quotient relation, while finiteness of the graph and exclusion of critical energies prevent infinitely many positive-length crossings in finite time. Borel measurability is checked on branch charts, and change of variables plus vertex flux cancellation proves invariance of the time measure.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

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Paper
arXiv:2606.05973v2
Authors listed
Philip Hierhager
Audit date
August 18, 2026
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